1. Field of the Invention
The present invention relates to a shock absorbing apparatus for a steering column in which an energy absorbing structure for damping a shock when a driver hits against a steering wheel during an emergency such as a collision can be made into a very simple structure, and which is capable of operating satisfactorily.
2. Description of the Related Art
As an apparatus for absorbing a shock during a collision of a vehicle so as to protect the driver from the shock, a carling type is conventionally widely used. For example, a shock apparatus for a steering column which has a very simple structure has been proposed in Japanese Patent Application Laid-Open No. 56041/1994. In addition, in Japanese Patent Application Laid-Open No. 93820/1993, there has also been proposed an apparatus which expands the variation of a load characteristic without substantially changing its structure by appropriately selecting an energy absorbing state during a collision.
In the above-described two shock absorbing apparatuses for a steering column, a protruding rib arranged in the longitudinal direction of the energy absorbing member is crushed by a through hole portion formed in the bracket which moves together with the steering column. In the case of such a structure, upper and lower portions of the through hole portion of the bracket serve to absorb an impact load by directly pressing and crushing the protruding rib of the energy absorbing member, while the left- and right-hand portions of the through hole portion serve to allow the bracket, which moves with the steering column, to move along the longitudinal direction of the energy absorbing member, or to directly deform the energy absorbing member. Accordingly, it is necessary to set the dimensional accuracy of both the vertical and horizontal dimensions of the through hole to high levels.
In addition, with the structure for damping the impact in the above-described steering apparatus, since the load varies depending on a dimensional change, strict dimensional accuracy is required in machining, so that machining efficiency deteriorates. Therefore, there is a drawback in that it is difficult to easily expand the variation of the load characteristic.